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From: Andrew Morton <akpm@linux-foundation.org>
To: Mark Pearson <devnull.port@googlemail.com>
Cc: sziwan@hell.org.pl, julia@diku.dk, corentincj@iksaif.net,
	sziwan@users.sourceforge.net,
	acpi4asus-user@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
	lenb@kernel.org
Subject: Re: [PATCH 2/9] drivers/acpi/asus_acpi.c: Correct use of ! and &
Date: Fri, 29 Feb 2008 13:33:20 -0800	[thread overview]
Message-ID: <20080229133320.1ec95e84.akpm@linux-foundation.org> (raw)
In-Reply-To: <47C849B8.1000902@googlemail.com>

On Fri, 29 Feb 2008 19:06:48 +0100
Mark Pearson <devnull.port@googlemail.com> wrote:

> Andrew Morton wrote:
> >> Seems an odd way of doing:
> >>
> >> 	led_out ^= 0x01;
> > 
> > It does.
> > 
> >> It this due to some optimisation?
> > 
> > Surely not ;)
> >
> ;) Thought so - one doesn't like to be too presumptuous ;)
> 
> > That code has been there for many years.
> > 
> > I changed the patch to this:
> > 
> > --- a/drivers/acpi/asus_acpi.c~drivers-acpi-asus_acpic-correct-use-of-and
> > +++ a/drivers/acpi/asus_acpi.c
> > @@ -610,7 +610,7 @@ write_led(const char __user * buffer, un
> >  	    (led_out) ? (hotk->status | ledmask) : (hotk->status & ~ledmask);
> >  
> >  	if (invert)		/* invert target value */
> > -		led_out = !led_out & 0x1;
> > +		led_out = !led_out;
> >  
> >  	if (!write_acpi_int(hotk->handle, ledname, led_out, NULL))
> >  		printk(KERN_WARNING "Asus ACPI: LED (%s) write failed\n",
> > _
> > 
> > 
> 
> Is the ! operator architecture/compiler dependent?

It shouldn't be.

> or can one always say that
> !NON_ZERO_VALUE == 0 and !0 == 1?
> 

I always have ;)  I expect it's in the C standard somewhere.

      reply	other threads:[~2008-02-29 21:49 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-26 20:42 Julia Lawall
2008-02-27 17:03 ` Karol Kozimor
2008-02-27 17:41   ` Julia Lawall
2008-02-27 18:29   ` Mark Pearson
2008-02-29  5:55     ` Andrew Morton
2008-02-29  6:10       ` Matthew Wilcox
2008-02-29  6:14         ` Matthew Wilcox
2008-02-29  6:19         ` Andrew Morton
2008-02-29 11:01       ` Julia Lawall
2008-02-29 11:08         ` Andrew Morton
2008-02-29 18:06       ` Mark Pearson
2008-02-29 21:33         ` Andrew Morton [this message]

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